A method of extracting some of the air compressed in a gas turbine compressor, cooling the air by a cooler, boosting the air by a boost compressor, and using the air as cooling air is known in order to cool high temperature components such as a gas turbine combustor, a turbine blade, and the like.
For example, Patent Citation 1 discloses that it is necessary to boost the air discharged from the compressor by the boost compressor, in a closed cooling type gas turbine which collects, in the combustor, cooling air used for cooling high temperature parts of a turbine and uses the air as combustion air. In addition, Patent Citation 1 also discloses that if the boost compressor boosts the coo hug air, the temperature of the cooling air is increased, and thus, a cooler for causing the temperature of the cooling air to be an appropriate temperature is provided.